Determining the Local Determining the Local Implications of Global Warming Implications of Global Warming

Clifford Mass

University of Washington

Global Warming 101

The Earth With No Atmosphere

(infrared)

Earth’s surface would be 60F cooler than today…no life.

But the Earth has an atmosphere!

• Includes gases such as nitrogen and oxygen

• Also includes greenhouse gases.

What is a Greenhouse Gas?• Greenhouse gas is a gas that that is relatively

transparent to solar radiation, but absorbs and emits in the infrared…the type of radiation the earth emits.

• Some examples:– Water vapor– Carbon dioxide– Nitrous oxide– Methane

Earth With An Atmosphere That Includes Greenhouse Gases

Partly

Greenhouse Gases Make the Earth Warmer by Slowing the Loss of Infrared Radiation

(infrared)

Greenhouse Gases Warm the Earth in a Similar Way That Blankets Warm Us at Night

The Problem: Rapidly Rising Greenhouse Gases Due to Mankind

Gases Trapped in Ice Gives Us a History of the Gases in the Atmosphere

But it is worse than that…

• There are a number of natural “amplifiers” of mankind’s emission of greenhouse gases.

• The warming due to increased carbon dioxide, methane, and other greenhouse gases will cause more water to be evaporated from the earth’s oceans.

Amplifier• The amount of evaporation increases with

temperature.

• Water vapor is the most potent greenhouse gas and thus causes even MORE warming.

• This produces a positive feedback.

But it gets even worse…

• Warming temperatures melt snow and ice.• Snow and ice help cool the planet because they

reflect much of the sun’s radiation….that is why you need sun glasses while skiing.

• As the snow melts less radiation is reflected to space and more is absorbed.

• Thus, the earth gets warmer, which melts more snow.

• Another positive feedback!

Is Global Warming Already Happening?

• Finding the global warming signal is made more difficult because the earth’s climate has a certain amount of natural variability.

• Also the warming due to man was relatively small before the middle of last century before the large increase in fossil fuel usage.

• The consensus of most atmospheric scientists is that some global warming signal due to man is now evident.

Eleven of the twelve warmest years in the past 150 years have occurred in the past twelve years (1995-2006)

These photographs, taken in 1928 and 2000, show how South Cascade Glacier in the Washington Cascade Mountains has retreated over time.

But what about the future?

The Technology of Prediction• Atmospheric scientists use complex climate

prediction models…called General Circulation Models…GCMS…to predict the future climate.

• These models are similar to weather forecast models, but allow the gases in the atmosphere to change.

• They also simulate the evolution of the oceans.• Have to assume the future emission of greenhouse

gases by mankind…a major uncertainty.• These models are not perfect and cannot exactly

replicate the current climate….but they are close and getting better each year.

Details on Current Study: GCM

IPCC Report, 2001IPCC Report, 2001

• Which Scenario Will Mankind Follow?

IPCC.AR4.2007

Sample Climate Model Output for 2100

What about the Northwest?

• Several of us are applying very high resolution simulations forced by the global climate model predictions

• Gives a view of the local implications of global warming.

• Could our mountains and other local features make it worse or better?

•Northwest weather is dominated by terrain and land-water contrasts of much smaller scale.•In order to understand the implications of global changes on our weather, we must consider our local terrain and land use.

Running High Resolution Regional Climate Models• 135, 45, 15 km MM5 domains

• Need 15 km grid spacing to model local weather features.

Solar Radiation

Snow and Ice Reflect Much of The Incoming Solar Radiation

Now

Solar Radiation

Global Warming Causes Snow level to Rise Resulting In Absorption of Solar Energy on Melted Slopes

=WARMINGFuture

Why Relative Cooling West of Cascades in Spring?

• Low clouds due to more onshore flow from off the cool, cloud Pacific.

• The Montereyization of the western lowlands!

Large Drop in Snowpack in the Mountains

Key Facts

• The overwhelming majority of atmospheric scientists believe global warming forced by mankind’s changes to the atmosphere has occurred and will became MUCH larger during the next decade.

• This is based on the best technology and observations available.

• There are substantial uncertainties, so we can’t give a specific number, but a range.

• Even if increases in the emission of greenhouse gases stop today, a certain amount of global warming is inevitable.

Range of Global Warming

Global Warming Goes Politicaland Reaches the Public Arena

Inconvenient Truth: Basically Accurate But Contains Some Errors

Downplays Global

Warming:Full of Major

Errors

The Day After Tomorrow: Global Warming Causes Ice Age:

Complete Nonsense

Mayor Nickels and Global Warming

• Claims of a 50% reduction in Cascade snowpack due to global warming are simply not true.

• Perhaps 10-15%

Bottom Line

• Global warming and its local implications are very serious.

• There are significant uncertainties, but they are NOT in whether global warming will occur, but rather the magnitude and its local effects.

The End

Why Such Strong Warming on Mountain Slopes..Particularly in

Spring?

• Probable Answer: Snow melt resulting in more solar heating.

Change inWaterOfSnowpack(%)

Precipitation

• Bottom Line: Annual trends relatively small, but some seasonal shifts

Early fall sees the greatest enhancement